DESCRIPTION: Applicant's Abstract Bartonella henselae is an opportunistic pathogen that causes disease in AIDS patients and intravenous drug abusers. Diagnosis of disease would be enhanced if a specific antigen could be identified. To this end the following aims have been identified. Aim 1: To identify genes encoding major antigens of B. henselae. A DNA lambda phage library will be screened with HIV-1 infected patient sera that are positive by indirect fluorescence assay (IFA) to Bartonella spp. Clones will be rescued and expressed in E. Coli. Aim 2: Determine the nucleotide sequence and control mechanisms of the gene coding for the antigen. Vector specific primers and exonuclease digestion of the insert will be used with dideoxynucleotide chain termination sequencing. Aim 3: Evaluate the diagnostic potential of the recombinant protein and its associated gene. Purified protein will be used as an antigen in ELISA assay. Aim 4: Determine the location, arrangement, and function of the antigen. Mutations of the gene will be transferred to B. henselae by conjugation with E. Coli.